Effect of captopril on 99mTc-diethylenetriaminepentaacetic acid renograms in two-kidney, one clip hypertension.

Abstract

SUMMARYIn an effort to improve on the noninvasive detection of renal artery stenosis, we investigated the effect of angiotensin converting enzyme inhibition on computer-assisted Tc-diethylenetriaminepentaacetic acid (DTPA) renal flow studies in a canine model of two-kidney, one clip hypertension and compared these findings with clearances of inulin and p-aminohippuric acid in the stenotic and contralateral kidney before and after converting enzyme inhibition. The T c -D T P A renal flow study with the converting enzyme inhibitor captopril (1.5 mg/kg bolus with 1.5 mg/min infusion) showed an increased sensitivity in the detection of unilateral renal artery stenosis over the use of the T c -D T P A study alone. Captopril induced striking alterations that were most evident in the 15-minute T c -D T P A renal flow study, in which all nine curves exhibited severely blunted uptake and excretion of the radionuclide. These changes were reversed during a recovery study without converting enzyme inhibition and were not seen when blood pressure was lowered with nitroprusside to a level similar to that observed during converting enzyme inhibition We reported the development of a computer-assisted Tc-diethylenetriaminepentaacetic acid (DTPA) renal flow study in a group of patients with angiographically proven RVHT and preserved renal function 3 and in a canine model of two-kidney, one clipFrom the

Renal scintigraphic captopril test in the diagnosis of renovascular hypertension.

“…• " However, the finding of clear renographic and morphological abnormalities suggestive of functional impairment in the kidney ipsilateral to the stenosis (i.e., flattening or disappearance of Phase 2 and 3 of the renal curve) in the majority of the patients with positive RSCT results seems to indicate, at least in our series, a predominant effect of captopril on the affected kidney. Similar observations were recently reported by Nally et al 9 in a canine model of two-kidney, one clip hypertension. Finally, the observation reported by Textor et al , 20 of an average, significant reduction of overall GFR by 25% after short-term captopril administration in renovascular hypertension, would further suggest that, at least acutely, in this disease the negative effect on GFR of the stenosed kidney outweighs the positive effect on the contralateral kidney.…”

Influence of Anaesthesia on Renal Hippurate Handling during Angiotensin-Converting Enzyme Inhibition in Unilateral Renal Artery Stenosis

“…In comparable studies with dogs un der PB anesthesia, others were able to dem onstrate a difference in tracer handling dur ing ACEi between the stenotic and nonste notic kidney [3,5], The discrepancy between these studies and ours could be caused by a difference in the severity of the stenosis. In our study the reduction in renal blood flow was induced during conciousness whereas in the other studies this took place during PB anesthesia.…”

“…The enhancement of the signs of a renal artery stenosis on the renogram by ACEi in general could be caused by effects on the renal perfusion pres sure exactly opposite to those described above for anesthesia: ACEi leads to a de crease in systemic blood pressure, but to an even larger decrease in perfusion pressure in the stenotic kidney since renal vascular resis tance decreases as well. The above hypothe sis not only explains our findings, namely the effects of anesthesia on the renogram being opposite to those of ACEi, but it also explains why the effects of ACEi in the situa tion of renal artery stenosis are greater than the effects of other blood-pressure-lowering drugs that do not directly influence renal vascular resistance [5], In summary, our data suggest that gen eral anesthesia attenuates the ACEi-induced delayed hippurate handling by a kidney be hind a moderate stenosis, probably due to enhancement of the sympathetic nervous system, which causes renal vascular resis tance and systemic blood pressure to rise. This may indicate that the presence of typi cal signs for a renal artery stenosis on a reno gram depends on a critically low level of CONSCIOUS PB ANESTHESIA Time (min) Fig.…”

Angiotensin converting enzyme inhibition improves diagnostic procedures for renovascular hypertension in dogs.

“…The present study shows that changes in neither RBF nor systemic blood pressure play a critical role. A possible causative role for the decrease in blood pressure caused by ACE inhibition was made unlikely by a former study 4 in which a blood pressure decrease obtained with nitroprusside did not cause changes in radionuclide studies, whereas a similar decrease with captopril did. The well-known decrease in poststenotic glomerular filtration rate may be responsible for the decreased excretion of the different trace materials.…”